The operations of launching and recovering a marine or submarine device from or to a support vessel also responsible for the transportation of the device generally include a critical phase, especially in a choppy sea conditions. That phase consists in the passage from the totally out of the water state in which the device is fastened to a handling means employed by the launch and recovery system to the totally submerged state in which the device no longer has any connection with the handling means of the launch and recovery system, and vice versa. In fact, it is during these critical phases that the ocean swell is the most dangerous to the integrity of the device, the device being agitated by the motion swell when it is close either to the structure of the vessel or to that of the lifting and handling means of the launch and recovery system, with the attendant risk of striking the vessel and/or the launch and recovery system. This is the case in particular for a marine or submarine device in the launch or recovery phase when the device is partly in the water. In this regard, the device movements are not yet (or no longer) completely controlled by the lifting and handling means of the launch and recovery system.
Accordingly, where autonomous devices, not towed by the vessel, are concerned, one known solution consists in providing mooring means on the hull of the device, for example securing means, said securing means being such that the device can be lifted whilst remaining in a horizontal position. Launching and recovery can then be carried out using a winch mounted on a mobile gantry placed at the stern of the vessel, for example, or a crane, the gantry or the crane making it possible to position the lifting winch over the recovery area. Thereafter launching and raising are effected vertically, which limits the possibilities of collision with the vessel during raising or lowering. Alternatively, the device can be lifted by placing it in a cradle type device itself including appropriate securing points.
This type of solution is applicable, notably autonomously, to devices towed from the center but is not easily applicable to devices towed from the front, however, in that, for obvious reasons of efficacy, the aim is to tow and to handle the device using a single cable. Handling by means such as those described above using a single cable proves delicate because it leads to the device passing from the vertical position to the horizontal position during launch and conversely during recovery. This handling moreover necessitates complementary operations the object of which is, after the device is lifted and positioned above the deck of the vessel, to deposit the device flat on the deck of the vessel or more generally in a storage area. These operations generally necessitate the intervention of human operatives, which intervention is rendered more delicate and more dangerous in a heavy sea. In the case of devices towed from the front, the solution that is generally preferred consists in using a handling cable temporarily attached above the center of gravity of the device.
A solution that is also used provides handling based on the placement of means including an inclined ramp on which the device slides onto the surface of the water or to leave it and return to the vessel. The ramp is generally configured to guide the device along a rectilinear trajectory, which prevents the device from being able to move laterally. However, a ramp of this kind is not generally suitable for use in a heavy sea: lateral movements of the device can then damage the ramp.
Using such means advantageously makes it possible to launch and to deploy the device behind the vessel by allowing the towing cable to play out and, conversely, to recover the device on board the vessel by winding in the cable, for example onto the drum of a winch. In this way the device towed by the vessel can be launched and recovered when the vessel is moving so that the device is naturally positioned on the axis of forward movement of the vessel.
Various solutions have been developed to alleviate these problems of coming into contact, generally suited to a given type of device. These known solutions generally consists in reinforcing the structure of the device, principally the nose, so that the nose resists impacts following entry into contact with the end of the ramp. It also consists in using means for minimizing these impacts, in particular configuring the ramp so that an end of the ramp is situated below the surface of the water so that the device floating on the surface comes into contact with an inclined surface of the ramp and not the end of the ramp. Solutions of this kind nevertheless prove inadequate in a heavy sea because of a slamming effect of the waves is accentuated by the movement of the vessel.
Other solutions have been developed (see for example EP 20110793422 and U.S. Pat. No. 8,430,049B1) in which the vessel incorporates a tiltable articulated ramp. The inclination of the ramp makes it possible to control the submerged part of the ramp. Once the ramp is submerged, the device is towed over an abutment that separates the ramp from the surface of the water. Moreover, in a heavy sea the ramp may come out of the water.
The foregoing solution is effective but cannot be fitted to all vessels. In fact, many vessels cannot support a weight necessary for installation of the equipment linked to the operation of a tiltable articulated ramp. The problem solved by the present invention is to cause the marine or submarine device to pass over a step situated between the end of the ramp and the water, notably when a small vessel is used, for example less than 50 meters long and preferably less than 20 meters long, incapable of supporting the installation of equipment that is too heavy, such as a tiltable articulated ramp as described in the prior art.